Glass substrates are used in a variety of applications such as automotive applications, architectural applications, aerospace applications, etc. Depending on the end use of the glass substrate, it will be desirable for the glass substrate to exhibit certain (a) aesthetic properties, such as, but not limited to, color and (b) solar control properties, such as, but not limited to, total solar energy transmittance (“TSET”), infrared transmittance and ultraviolet transmittance.
For example, glass substrates are used in automotive applications as automotive vision panels (i.e., front windows, sidelights, etc.). Automotive vision panels need to exhibit a desirable color. At present, desirable colors for automotive vision panels include blue, green and gray. Further, if the automotive vision panel is used as a front windshield in a vehicle driven in the United States, it will have to exhibit a visible light transmittance (“Lta”) of equal to or greater than 70%. Countries other than the United States have different Lta requirements for front windshields.
One of the ways the aesthetic properties and solar control properties of a glass substrate can be modified involves changing the chemical composition (i.e., the type of materials that make up the glass composition and/or the weight percentages of the various materials in the glass composition) of the glass substrate. Oftentimes, colorants and/or other materials capable of modifying the solar properties of a glass composition are added to a well known base glass composition such as a soda-lime-silica base glass composition to provide a glass substrate capable of exhibiting unique performance properties. Although the effect of one colorant or one material capable of modifying the solar properties of a glass composition may be known (for example, it is known that adding FeO to a base glass composition increases the infrared (IR) absorption of the glass composition), it is the essence of invention to use various colorants and/or materials capable of modifying the solar properties of a glass composition, each colorant or material capable of producing a unique effect individually, to collectively achieve a combination of performance properties.
According to the present invention, novel materials are added in novel amounts to a soda-lime-silica base glass composition to provide glass substrates capable of exhibiting the desired aesthetic and solar control properties. The combination of desired aesthetic and solar control properties realized by the glass composition in a substrate at a thickness of 3.9 mm (0.1535 inches) of the present invention are as follows:
1. a neutral gray color characterized by a dominant wavelength in the range of 480 to 580 nanometers and an excitation purity of equal to or less than 8%;
2. a visible light transmittance (Lta) of 60% or greater;
3. a total solar infrared transmittance (TSIR) equal to or less than 40%;
4. a total solar energy transmittance (TSET) equal to or less than 60%; and
5. a total solar ultraviolet transmittance (ISOUV) of equal to or less than 30%.